As the ink-jet printing field develops, improvements in printing characteristics such as edge acuity, optical density, substrate adherence, dry time, resolution, durability, and waterfastness continue to be explored. At the same time, while trying to improve upon these characteristics, fluids of the ink-jet system should also provide long term storage compositional stability and long term reliability without equipment corrosion or nozzle clogging. Though the above lists of characteristics provide a worthy goal, there are difficulties associated with satisfying all of the above characteristics. Often, the inclusion of an ink component meant to satisfy one of the above characteristics can prevent another characteristic from being met. Thus, most commercial inks for use in ink-jet printers represent a compromise in an attempt to achieve at least an adequate response in meeting all of the above listed objectives.
Various substances have been used to formulate ink-jet inks and other recording solutions in an attempt to meet the above objectives. Some of these substances which have been included are pigments and/or dyes to provide color to the image, water and/or water-soluble organic solvents to provide a liquid composition that functions properly within ink-jet equipment, surfactants of various ionic character to provide decreased surface tension at various liquid interfaces, dispersants for enhancing solubility characteristics, and various other solution characteristic modifiers such as viscosity modifiers, pH adjustors, antiseptics, antioxidants, chelating agents, biocides, and the like.
Printing media has also been modified to utilize a variety of substances, including various binding materials to improve recording parameters. These binding materials can include inorganic porous coatings, such as silica and alumina, or swellable organic coatings, such as gelatins and other similar compositions. These materials can be coated on a paper or other substrate to provide improvement in image quality when an ink-jet ink is printed thereon, as is generally known in the art.
In general, ink-jet inks are either dye- or pigment-based inks. Both are typically prepared in an ink vehicle that contains the dye and/or the pigment. Dye-based ink-jet inks generally use a liquid dye that is usually water-based to turn the media a specific color. Conversely, pigmented inks typically use a solid or dispersed dye to achieve color.
Color characteristics, water fastness, and humid fastness of dye-containing inks play an important role in the quality of the printed ink-jet image. Perceived color quality can be characterized using any one of several color space systems, such as CIELAB or Munsell, as is well known in the art. Though dye-based ink-jet inks can provide good color characteristics, water fastness and humid fastness of printed images, particularly on porous media, can remain a challenge, as exposure to water or humidity after printing can cause color shift and/or dye migration, for example.
As a result of the state of the art, it would be desirable to provide dye structures and ink-jet inks containing those dye structures that provide good color characteristics, and also provide good water fastness and humid fastness.